Scientists have flown clocks in jet aircraft and
on orbiting spacecraft and measured the slowing of their onboard
clocks by comparing them to clocks on the ground.

Around the world in 40 hours.

Compare watches with a friend as you leave San
Francisco on a round-the-world tour by jet. When you return you
compare watches again, They will agree to within the accuracy of the
watches. So it seems that Newtons idea that clocks run at the same at
all speeds and in all locations is correct.

However this very experiment was done in 1971
using very accurate atomic clocks (cesium beam) flying around the
world strapped to the wall in coach class in a 707
airliner.

The experimenters were J.C.. Hafele of Washington
University, and Richard Keating of the U.S. Naval
Observatory.

Images: experimenters, 707, atomic
clock

Use this one it is simpler

In another experiment, on November 22, 1975 a U.S.
Navy P3C Orion aircraft flew back and forth for 15 hours at altitudes
between 25,000 and 35,000 feet (7,600 meters to 10,600 meters) over
Chesapeake Bay. The experimenter was Carroll Alley the plane flew at
270 knots or 140 m/s and clocks were compared on the plane and on the
ground by laser signal.

The clocks lost 5.6 nanoseconds during this 15
hour flight, as predicted by Special Relativity. The plane flew at
4.7 x 10^-7 c.

If we imagine a version of this experiment in
which the plane flew around in a circle over us for the same 40 hours
it took to fly around the world then the following calculation can be
done.

In 40 hours of flying at 550 miles per hour the
flying clock ran slower and measured less time than the clock on the
ground.

Frequent Flyer
Seconds enter the number of frequent flyer
miles you have flown in your life ( between 0 and 100,000,000) print
out the number of seconds your watch has lost as viewed by a
stationary observer on the ground.

convert m miles into hours h into seconds
t then multiply by 3 * 10^-13

55,000 miles will save you 0.1
microsecond

There is another effect from general relativity
that also affects this experiment, clocks run slow when the
acceleration is higher, so near the surface of the earth where the
acceleration of gravity is higher than in an airplane clocks run
slower, this effect was also observed during the round the world
flight, but we're not dealing with general relativity on this web
page.

GPS clocks in space

GPS

There are 24 satellites orbiting the earth as part
of the Global Positioning Satellite navigation system.

These satellites have atomic clocks on
board,

Receivers on earth use signals from these
satellites to determine the location of the receiver on the earth.
The satellites circle the earth twice per day at an altitude of
20,000 km and at a speed of 14,000 km/hr or 3.9 km/s or 3.9 * 10^3
m/s

Because the atomic clocks are moving relative to
the surface of the earth, and because the satellites are in orbit
high above the earth the clocks must be adjusted for the effects of
special relativity as well as general relativity.

A moving clock appears to run slow in special
relativity. The GPS satellites are orbiting at a speed that is fast
enough to make the clock lose 7,000 nanoseconds a day. This would
lead to an error in the location of the receiver on the ground of
7000 feet or about 1.5 miles per day.

A moving clock appears to run fast when it is in a
lower gravity environment. The clocks run fast so that they gain
about 45,000 nanoseconds a day due to general relativity. The
combination of the gain from general relativity and the loss for
special relativity would create an error of about 38,000 ns or 7
miles per day if corrections were not made.

The first GPS satellite was launched without the
relativity correction program operating. The data showed that
Einstein's theories predicted the changing clock rates of the GPS
satellites within the errors of the measurements. The engineers then
turned on the correction program.